High-pressure piston.



H. LED/IP.

HIGH PRESSURE PISTON. APPLICATION FILED IuLY2I. 1914.

Patented Api'. 25, 1916.

' to the metal of which the cylinderis made.

I' sheath or jacket or bushing of the soft metal n HERMANN LEMJP, 0FERIE, PENNSYLVANIA, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A. CORPORATION0F NEW YORK.

HIGH-PRESSURE PISTON.

Specification of Letters Jlatent.S

Patented dpr. 25,1l91lt5.

pression internal combustion engines, to furnish the blast air forinjecting the liquid fuel into the engine cylinder. This air iscompressed to a pressure of from'900 to 1200 lpounds tothe square inch,so that great care must be exercised in packing the piston in vthe finalstage of the pump. Owing to the small size of the piston, which iscommonly from one and one-half to two inches in dianieter, it isimpracticable to use split packing rings sprung into grooves. llnsteadof this, the piston has a separable head pro- Avidedat one end with atenonsecured in a socket in the end of the piston and having atits-other end a flange to clamp a plurality of split spring packingrings and spacers lying between said iange and the end of the piston. Itrequires nice workmanship to lit these small pistons accurately and havethem exactly co-axial with the low pressure 'pistons.; both high and lowpressure pistons being usually integral or fastened together, and theircylinders having `their axes 1n line.. If the clearances between thepistons and the cylinders are not made just right, there is Y(danger ofthe pistons seizing and wrecking the pum` in case the cooling Watershould fail; there y involvingcostly delays and the expense of newmachinery.

'Fha object of the present invention is to minimize .the possibility of`such accidents, and to reduce the time necessary 'for repairs.

WVithl these ends in view, lthe invention comprises a solid pistonfitting tightly 1n the cylinder and having awearing surface of metalwhich is relatively soft with respect l prefer to use a coreof steelhaving a thick suitably secured thereto. The pressure of the compressedair on the end ofthe piston has a packing effect on the soft metalbushing, causing it to t the cylinder tightly and to accommodateitself'to any expansion or contraction. The soft metal ll prefer to useis Babbitt metal, which has a melting point between 400 and 500 degreesFahrenheit, depending upon the ingredients used and their proportions.

In the accompanying drawing, Figure 1 is a vertical section of areciprocating twostage air compressor embodying my invention. Fig. 2 isa sectional elevation of the preferred construction of the piston, on anenlarged scale, and Fig. 3 is a similar view of the modification shownin Fig. 1.

rlhe compressor is of the usual construe'- tion, having a power-drivenshaft 1 containing a crank 2 which is connected by a rod 3 with a trunkpiston 4 working in a cylinder 5 and constituting the first or lowpressure stage `of the pump. Axially in line with the cylinder 5 is thehigh pressure cylinder 6, much smaller Ain diameter. Rising centrallyfrom the head of the piston 4 is a neck 7 forming a socket to receive atenon 8 on a solid piston 9 of steel. The tenon projects into the hollowtrunk piston 4 and is screw-threadedto receive the fastening and locknutslO, l1. The outerportion 12 of the-piston 9 is reduced in diametera'nd is given a rough or. irregular surface, .preferably a series ofcircumferential grooves .13.

The upper end of the portion 12 is preferably conical, Vthe inclinationof the sides being preferably at about 45 degrees to the axls of thepiston.' Thisreduced portion 12l of the piston serves as al core for ahead 14 of relatively soft metal, preferably babbitt, which is cast uponand around it, and is then turned ydown to the proper size by centeringthe steel piston in a lathe; the .recessI 15 kfor the lathe center beingleft for this purpose. The outside diameter of the Babbitt head is saythree one-hundredths of an inch larger than the piston 9 so that it fitstightly in the cylinder. The heavy pressure of the hot compressed airforcing the soft metal againstthe conical tip of the core 12, ycausessaid metal to expand and make close and. air tight contact with thewalls of the cylinder.

Experience has provedthe lvery satisfactory service which this devicelwill render, and furthermore, that if by failure of the cooling Water,the machine gets 'so hot as to melt the babbitt, the only damage done isto the piston head, Which can be replaced, all repairs made, and themachine started up again, With not over one days delay.

Figs. 1 and 3 shov;7 hoW my invention can be applied to many existingpumps. The body 16 of the piston is of about the combined length of theneck 7 and piston 9 shown in Fig. 2, and has a central socketintersected by a transverse slot 17. The piston head commonly usedheretofore has a slotted tenon fitting said socket, in which it isfastened by a taper key. This is the construction outlined in theopening paragraphs of this specification. To adapt my invention to thisstructure, I make use of a grooved core 18 with a head of Babbitt metal19 cast on it and a tenon 2O fitting the socket in the piston and havinga transverse slot' to register With the slot 17- in the piston andreceive the fastening key 21. Y

In accordance with the provisions of the patent statutes, I havedescribed the principle of operation ofmy invention, together with theapparatus which I now considerJ to represent the best embodimentthereof; but I desire to have it understood that the apparatus shown isonly illustrative, and that the invention can 'be carried out by othermeans.

What I claim as newA and desire to secure by Letters Patent of theUnited States, is:

1. The combination With a cylinder, of a piston therein comprising ahead having a core of hard metal and a bushing of soft metal, saidbushing being adapted to t closely the cylinder wall.

2. A piston head for a high pressure air pump, composed -of a roughenedHard metal core and a bushing of babbitt cast thereon.

3. The combination with the high pressure cylinder of a multistage aircompressor, of a piston having a steel head faced With babbitt andtightly fitting said cylinder.

4. In a high pressure fluid pump, the combination of a cylinder, and a'piston which moves therein, said piston having a head comprising a coreof hard metal and a facing of softer metal, said facing of softer metalbeing adapted to be expanded on the hard metal by the pressure of thefluid being-pumped so as to bring it into close conl tact with thecylinder Wall.

5. A piston head having a grooved steel core provided with a conicaltip, and a bushing of soft metal inclosing said core.

In Witness whereof, I have hereunto set my hand this 18th day of July,1914.

HERMANN LEMP.

Witnesses: I

OTTO F. PERssoN, O. T. FOUCHE.

